From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f202.google.com (mail-pf1-f202.google.com [209.85.210.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BE50728E7 for ; Wed, 26 Jun 2024 05:08:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719378505; cv=none; b=lL8YFLAJ9Gy5v8K+TNjwjQkdqwMcAdK4fJpmsurlDHa3+flej3PUbE3/v3yvg/SBgTleSjgUHz5wxFZUw5xsvMkIiLvmRI5HT6XDEejLJyqAsLm5o+duin6OngbGLQ5jhOR7DWNrQW4PHQCzitAjwQjankF+460/+iPk4ldeSWc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719378505; c=relaxed/simple; bh=jeEuRsnMW42UDJL4uCR8Lby79ZLU5/csNxUpONX88SY=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=L4HojHiittq7I7B3njF2hgqY+OMYb/T/S3pH8T3OarExTYnm44+s9AMLytaDKehgvf8klcMEqCa+k306x5XBJ7KyUv2UMBf2Z1UWkfECem5ZXsBtiPBOX8ntywT8geZTp9o+is5rxg1CiL4Da9rl/BC/bhma+7lJjSECxqotL3w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--jiaqiyan.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=yJQpeAbR; arc=none smtp.client-ip=209.85.210.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jiaqiyan.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="yJQpeAbR" Received: by mail-pf1-f202.google.com with SMTP id d2e1a72fcca58-7065df788f7so227492b3a.0 for ; Tue, 25 Jun 2024 22:08:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1719378503; x=1719983303; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=CGDqphXBU6R+lNPyRUopWgvG7yuYFqi637jqIyNGWis=; b=yJQpeAbRG4C/W/M3+obLA27dCf43xhbJ03KYX/s+qr5vdtZftfuXAfUKHqqrEWl/Rz bDbhgqiDJbqug826WCOuW8QmzyCGtOgxXynR1nF77WoR+GhqxN//Yvj8B5/Wg80CxGgL GVJVdL7wPvnXYcyJybI0gfWhr+yNrwz6P2wOOSru5hPyDg8shDCVIe7Z/reVxwLvQH5b xxzUyjJ/Ue/HafxAjQuBI2JdJSblhOlqPjiGqoLb08DmZRlql4KDkl9D34CKtZgYD93Y sMSmT+5ubnCcV1wWAQxeT8oje/S5KRdgw11JdSLcud4hfG1EZA0aZCCHUZfqPRPxFPn6 AvmQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1719378503; x=1719983303; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=CGDqphXBU6R+lNPyRUopWgvG7yuYFqi637jqIyNGWis=; b=Fgxlx8irjiI88KYc0Wf+Bq+BLdYIKp86SfP0xQkCQoEvhyC2CFD3i9szTBDtPYLjTQ zBeHycKLCD/usASZgoaBt+UDvpDSFxaE0hDtHAvTkbpatjoErC/IgODqYEm1SxgtYYJ0 yZs3a88oPMPLHLn8abYoXCfIH63snsgSh36LfvIpinMz/TdtZfhTCPk3evx/Q3SohstQ 4hau+Tc8zC0xeT38CVzPwq3GzbYpfe6OTGIYtsNVbS0/o6iZrQdvvW3kB7RZ69ksSgQE xLI+i5ID+Qy/obQZcCqPKVLbNxdHf1GPQr28aCitvqPSJNveWGIjC+R/9Umkslv3T8Fc 3wyg== X-Forwarded-Encrypted: i=1; AJvYcCUfpJOjFPZ/oGQiuBQpyfuV3AYbk1iX+AqRYEefEPjaLwcWsLYMrnFnzr6V9YLPmD13o+1xIiaf6jwMU2lbcDziU3u2CVzdWq7tJOHUMHiI X-Gm-Message-State: AOJu0YwBXqb9eRbhHMwFQBjRKX02AY4q02IdZIpwWqr4mSXxpDALIcxO eCBBT2/NRAf1J15OeY2a/D+CHnKgJIEM8CXiSZyOE9awAS/E9Vp/lIpZ2i3tqWxAAZoNIOC/ds+ YfdMjd5ZZJA== X-Google-Smtp-Source: AGHT+IFb+0VOH/8Ji5MJY9Uzpp2NjXzdjAP0KEkJlwDoF3zvJdDZjjCYpaexBLDLoxcxVDGz7IEJNGYV1Aobyw== X-Received: from yjq3.c.googlers.com ([fda3:e722:ac3:cc00:24:72f4:c0a8:272f]) (user=jiaqiyan job=sendgmr) by 2002:a05:6a00:4309:b0:705:d750:83dd with SMTP id d2e1a72fcca58-70669e5e132mr340822b3a.0.1719378502937; Tue, 25 Jun 2024 22:08:22 -0700 (PDT) Date: Wed, 26 Jun 2024 05:08:14 +0000 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.45.2.741.gdbec12cfda-goog Message-ID: <20240626050818.2277273-1-jiaqiyan@google.com> Subject: [PATCH v6 0/4] Userspace controls soft-offline pages From: Jiaqi Yan To: nao.horiguchi@gmail.com, linmiaohe@huawei.com Cc: jane.chu@oracle.com, rdunlap@infradead.org, ioworker0@gmail.com, muchun.song@linux.dev, akpm@linux-foundation.org, shuah@kernel.org, corbet@lwn.net, osalvador@suse.de, rientjes@google.com, duenwen@google.com, fvdl@google.com, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-doc@vger.kernel.org, Jiaqi Yan Content-Type: text/plain; charset="UTF-8" Correctable memory errors are very common on servers with large amount of memory, and are corrected by ECC, but with two pain points to users: 1. Correction usually happens on the fly and adds latency overhead 2. Not-fully-proved theory states excessive correctable memory errors can develop into uncorrectable memory error. Soft offline is kernel's additional solution for memory pages having (excessive) corrected memory errors. Impacted page is migrated to healthy page if it is in use, then the original page is discarded for any future use. The actual policy on whether (and when) to soft offline should be maintained by userspace, especially in case of an 1G HugeTLB page. Soft-offline dissolves the HugeTLB page, either in-use or free, into chunks of 4K pages, reducing HugeTLB pool capacity by 1 hugepage. If userspace has not acknowledged such behavior, it may be surprised when later mmap hugepages MAP_FAILED due to lack of hugepages. In case of a transparent hugepage, it will be split into 4K pages as well; userspace will stop enjoying the transparent performance. In addition, discarding the entire 1G HugeTLB page only because of corrected memory errors sounds very costly and kernel better not doing under the hood. But today there are at least 2 such cases: 1. GHES driver sees both GHES_SEV_CORRECTED and CPER_SEC_ERROR_THRESHOLD_EXCEEDED after parsing CPER. 2. RAS Correctable Errors Collector counts correctable errors per PFN and when the counter for a PFN reaches threshold In both cases, userspace has no control of the soft offline performed by kernel's memory failure recovery. This patch series give userspace the control of softofflining any page: kernel only soft offlines raw page / transparent hugepage / HugeTLB hugepage if userspace has agreed to. The interface to userspace is a new sysctl called enable_soft_offline under /proc/sys/vm. By default enable_soft_line is 1 to preserve existing behavior in kernel. Changelog v5=> v6: * incorporate feedbacks from Miaohe Lin * add a ':' in soft offline log. * close hugetlbfs file descriptor in selftest. * no need to "return" after ksft_exit_fail_msg. v4 => v5: * incorporate feedbacks from Muhammad Usama Anjum * refactor selftest to use what available in kselftest.h v3 => v4: * incorporate feedbacks from Miaohe Lin , Andrew Morton , and Oscar Salvador . * insert a refactor commit to unify soft offline's logs to follow "Soft offline: 0x${pfn}: ${message}" format. * some rewords in document: fail => will not perform. * v4 is still based on commit 83a7eefedc9b ("Linux 6.10-rc3"), akpm/mm-stable. v2 => v3: * incorporate feedbacks from Miaohe Lin , Lance Yang , Oscar Salvador , and David Rientjes . * release potential refcount if enable_soft_offline is 0. * soft_offline_page() returns EOPNOTSUPP if enable_soft_offline is 0. * refactor hugetlb-soft-offline.c, for example, introduce test_soft_offline_common to reduce repeated code. * rewrite enable_soft_offline's documentation, adds more details about the cost of soft-offline for transparent and hugetlb hugepages, and components that are impacted when enable_soft_offline becomes 0. * fix typos in commit messages. * v3 is still based on commit 83a7eefedc9b ("Linux 6.10-rc3"). v1 => v2: * incorporate feedbacks from both Miaohe Lin and Jane Chu . * make the switch to control all pages, instead of HugeTLB specific. * change the API from /sys/kernel/mm/hugepages/hugepages-${size}kB/softoffline_corrected_errors to /proc/sys/vm/enable_soft_offline. * minor update to test code. * update documentation of the user control API. * v2 is based on commit 83a7eefedc9b ("Linux 6.10-rc3"). Jiaqi Yan (4): mm/memory-failure: refactor log format in soft offline code mm/memory-failure: userspace controls soft-offlining pages selftest/mm: test enable_soft_offline behaviors docs: mm: add enable_soft_offline sysctl Documentation/admin-guide/sysctl/vm.rst | 32 +++ mm/memory-failure.c | 38 ++- tools/testing/selftests/mm/.gitignore | 1 + tools/testing/selftests/mm/Makefile | 1 + .../selftests/mm/hugetlb-soft-offline.c | 228 ++++++++++++++++++ tools/testing/selftests/mm/run_vmtests.sh | 4 + 6 files changed, 296 insertions(+), 8 deletions(-) create mode 100644 tools/testing/selftests/mm/hugetlb-soft-offline.c -- 2.45.2.741.gdbec12cfda-goog